quantum coherence in incommensurate systems
Researchers in Professor T.-C. Chiang's group have demonstrated that quantum coherence is possible in electronic systems that are incommensurate, thereby removing one obstacle in the development of quantum devices.
Electronic effects in thin films and at interfaces lie at the heart of modern solid-state electronic technology. As device dimensions shrink toward the nanoscale, quantum coherence and interference phenomena become increasingly important.
"At quantum dimensions, quantum mechanics says device components will couple together and act in a concerted manner, where everything affects everything else," said Chiang. "Most scientists assume that electronic layers must be commensurate, so electrons will flow without being diverted or scattered."
In fact, however, most material interfaces are incommensurate as a result of differences in crystal sizes, symmetries or atomic spacing. Random scattering of electrons was thought to destroy quantum coherence in such systems at the nanoscale.
Now, by studying electron fringe structure in silver films on highly doped silicon substrates, Chiang and his research group show that even when electronic layers are incommensurate, they can still be coherent. Although the silver films and silicon substrates are lattice mismatched and incommensurate, the wave functions are compatible and can be matched over the interface plane. The resulting state is coherent throughout the entire system. Read more...